This invention relates to a power fuse recloser apparatus and particularly to such a recloser having a remote mechanical operator which permits the workmen to remove themselves from the possible hazard area during reclosing of a power line fuse.
Power distribution systems employ various fuse structures for opening a circuit in response to abnormal and/or particularly dangerous power conditions. Fuse cutout structures are widely used in the service lines in power distribution and function to burn open and stop current flow in response to abnormal power line conditions, which are primarily predetermined overvoltage conditions. Such conditions are often caused by falling tree branches during a wind storm, lightening striking the lines or equipment, animals crossing the lines and various other abnormal conditions. The fuse cutout structures are generally constructed to release and drop from the fuse support or holder such that the lineman can readily locate the blown fuse. A widely employed fuse cutout structure includes a tubular cartridge fuse which is replaceably mounted within a pole or transformer mounted fuse holder. The fuse is specially constructed to open extremely rapidly to protect the power system components and the equipment connected to the power system, and in fact the fuse may open with an explosive characteristic. The fuse structures are generally formed with an outer insulating tubular shell with a fuse mechanism secured within the insulating shell and terminating at the opposite end in electrical contacts. The fuse holder includes an insulating support with end fuse contacts and connector members for connection to the line. The connector members are coupled to the opposite end fuse contacts to establish the electrical path between the power leads. Generally, the lower fuse contact is pivotally mounted in the lower connector of the fuse holder while the upper fuse contact includes a releasable latch mechanism to firmly support the fuse cartridge in place. When the fuse burns open, the entire assembly is released and drops under the force of gravity to an obvious and notable open position. The latch mechanism usually includes a release lever at the upper end for opening and closing the latch mechanism and thereby providing removal and insertion of the fuse through the use of a conventional switch pole. The latch structure is employed with a hook or switch pole to permit the linemen to effect the closing without actually engaging the fuse structure. The switch stick includes fuse support hooks secured to an insulating handle to isolate the workmen from the high power line connections to which the fuse cartridge is inserted. The fuse is generally constructed such that during the fuse opening, the gases generated within the fuse blow out the upper end of the tubular fuse cartridge. As a practical matter, the fuse may at times explode, disrupt the cartridge and even escape through the opposite or lower end of the fuse.
Under normal operating conditions, the linemen or other workmen can safely climb the pole and open or close the fuse. However, in new installations or once a fuse has blown, there is always the danger that during the fuse replacement an abnormal condition exists, may not have cleared itself or more than one abnormal condition may have existed and not all of them been located and cleared.
A particular occasion for creation of a hazardous condition in power line systems is an over-voltage line condition which is applied on a pole-mounted transformer or capacitor banks. For example, an over-voltage line condition may result in faulting a winding in an adjacent pole-mounted power transformer of the oil-filled type. Just before or just after the fuse senses an over-voltage line condition and before the fuse burns opens, such line condition may fault the transformer winding. The lineman cannot visually detect such fault. He must however mount the pole to replace the fuse and even though a fuse stick is used, the linesman is in a hazarad area. Thus, upon reclosure of the fuse, an arc is created at the fault point in the winding and thus within the insulating oil. Such arc produces an instantaneous energy release which may equal 25,000 B.T.U.'s per pound of oil. The result is often a large fireball reaching 25 to 20 feet down the pole and enveloping the power, wires, the cutout and other adjacent elements including linemen.
Although the hook pole and switch stick structures thus are widely employed and provide some degree of safety, the explosive characteristic of power line fuse reclosure is such that a severe hazard to the workmen is an ever present unknown danger. Thus, injuries and even deaths have been reported resulting from malfunctions during a fuse reclosing on a power line.
There is therefore a need for a remote recloser unit which will not only permit but preferably require the lineman to reclose the fuse from a relatively remote location so as to be located in a safe working distance, both horizontally and vertically, from the potentially explosive equipment. Such a device would provide a significant improved safety for linemen and others engaged in installing and servicing new and existing equipment and particularly servicing existing equipment which has been either taken out of service or blown a fuse as a result of line equipment malfunction and the like.